Latex coatings for electrostatic and photoconductive purposes

ABSTRACT

AN AQUEOUS LATEX COATING COMPOSITION COMPRISING AN INTERPOLYMER OF METHYL METHACRYLATE, BUTADIENE AND STYRENE AND HAVING DISSOLVED THEREIN FROM ABOUT 0.5 TO ABOUT 2.5 PERCENT BY WEIGHT OF THE SURFACTANT MIXTURE CONSISTING OF (1) A SALT SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL AND AMMONIUM SALTS OF ALKYL SULFATES, ALKYL ARYL SULFONATES AND MIXTURES THEREOF, AND (2) A SALT SELECTED FROM THE GROUP CONSISTING OF THE ALKALI METAL AND AMMONIUM SALTS OF FATTY ACIDS.

Filed Au 1. 1966 Jan. 26,1971 A.J. coLE ETAL 35 85544 m commasFOBELECTROSTATICAND PHbTOCONDUCTIVE PURPOSES I zshep ts-shee tl i i i fv 1 I BUTADIE NE FIG. 1.

. I ALBERT 1 001.51 GEORGE B ROWLAND Jan. 26, 1971 ilA'rEx COATINGS FORA. J. COLE ETAL ELECTROSTATIC AND PHOTOCQNDUCTiVE PURPOSES Filed Aug. 1.1966 aboo . zsoo 1. I goo VOLTSQIACCEPTED 2- yShaets-Sheet I 2 r 4 e 8IO l2 POUNDS /REAM ALBERT J. COLE GEORGE P. ROWLAND mvmons United StatesPatent LATEX COATINGS FOR ELECTROSTATIC AND PHOTOCONDUCTIVE PURPOSESAlbert J. Cole, New Hanover Township, Pa., and George P. Rowland, Akron,Ohio, assignors to The Firestone Tire & Rubber Company, Akron, Ohio, acorporation of Ohio Filed Aug. 1, 1966, Ser. No. 569,301 Int. Cl. C08d7/02; C09d 3/64 U.S. Cl. 26029.7 10 Claims ABSTRACT OF THE DISCLOSUREThis invention relates to sheets coated with a resinous methylmethacrylate, butadiene and styrene interpolymer. More particularly, itrelates to sheets useful in dry printing processes, i.e., electrostaticand Electrofax printing processes, and to processes for producing andusing such sheets. This invention also relates to coating compositionsuseful for preparing sheets useful in electrostatic and Electrofaxprocesses.

Electrostatic printing employs a sheet coated with a clear film,referred to hereinafter as an electrostatic sheet, which when subjectedto a corona discharge in certain predetermined areas, accepts a portionof the charge in those areas, and holds it for a period of timesufficient for a visible image to be developed on .he sheet. The imageis developed by depositing a toner (a pigmented, charged resin powder)on the surface of the coated sheet, which is attracted to those portionsof the coating on which a charge has been imposed. The toner may bedeposited by a so-called magnetic brus which is made by mixing the tonerpowder with iron particles (to give the toner the proper electrostaticcharge by the triboelectric effect) and holding the mixture on a magnet.As this brush is swept across the coated sheet, the toner particlesadhere to the charged areas while the iron particles are retained on themagnet. The sheet is then subjected to a temperature of approximately150 C. for a short period of time to fuse the toner powder to the sheet.

The Electrofax process employs a sheet, commonly referred to as a binderplate, coated with a photoconductive material, usually zinc oxide,disbursed in a binder. The sheet is given a negative charge in the darkby corona discharge, and then exposed to an image projected through alens system. Light from the non-image areas of the document copiedcauses the charge on the sheet to be dissipated in the correspondingareas, leaving on the sheet an electrostatic pattern that duplicates theimage of the original. This image may be developed using Patented Jan.26, 1971 the magnetic brush technique described above or by using aliquid development system which employs pigments particles suspended inan organic liquid. Using the liquid developer method, the developer isapplied on the sheet either by dipping the paper in the developer or byspraying the developer on the sheet. The suspended pigmented particlescling to the charged areas of the paper by etectrostatic attraction andare held to it permanently, usually by a resin binder. After most of theliquid has flowed off the sheet the remainder is normally removed byblowing warm air across it.

In sheets employed in electrostatic printing processes it is essentialthat the coated sheet accept a static electric charge and hold at leastpart of it for a period of time sufiicient for the latent image to bedeveloped.

Many polymers which would be acceptable for use as coatings forelectrostatic sheets or as binder for binder plates exhibit the propertyof sticking to an adjacent surface (blocking) when stacked or wound inrolls. This property necessitates the inclusion of an anti-bl0ckingagent in the polymer, and since many of the known antiblocking agentsarereadily ionizable, the conductivity of the coating may be effected.Thus, it is apparent that it is desirable that the polymer used as acoating for electrostatic sheets, or as a binder for binder plates, benonblocking.

At the present time, the most Widely used binder plates are made bycoating an organic solvent solution of a resin containing aphotoconductive material, such as zinc oxide, uniformly dispersedtherethrough onto a paper backing. Electrostatic sheets are generallymade in a similar manner, using similar organic solvent solutions absentthe photoconductive material. Such paper sheets are potentially no moreexpensive than high grade magazine paper. However, due in part to theexpenses inherent in using organic solvent systems, i.e., the expensesincurred due to the necessity of using special apparatus for solventrecovery and to minimize vapors and fumes, such relative low cost levelhas not been attained. Another disadvantage of organic solvent systemsis the inherent fire hazard presented. Attempts have been made toeliminate the organic solvents and apply the coating in an aqueoussystem. Such attempts have usually resulted in films having drasticallydiminished electrical insulating properties, reduced charge acceptanceand retention properties, or increased sensitivity to moisture.

It has now been found that electrostatic sheets and binder plates may beprepared using a novel aqueous latex as hereinafter described. Theaqueous coating system may be handled in conventional paper machinery toapply the coating to the paper web, using conventional techniques forhandling aqueous coating compositions. The novel aqueous latex of thepresent invention comprises an interpolymer of methyl methacrylate,butadiene, and styrene. Films formed from this latex exhibit a highdegree of charge acceptance and retention, are nonconductive, relativelyinsensitive to moisture, and are essentially non-blocking. Anotheradvantage of the latex of the present invention is that it may be formedusing relatively small amounts of emulsifier.

In order to form a non-blocking film from the latex it is essential thatthe ratio by weight of methyl methacrylate to butadiene to styrene beselected so that the amount of each monomer falls within the shaded areaof the ternary diagram of FIG. 1. By selecting monomer ratios so thatthey fall within the shaded area of the ternary diagram of FIG. 1, theresultant interpolymer will form a charge accepting, non-blocking film.The ratios defined by the shaded area of the diagram have beendetermined empirically. The diagram of FIG. 1 is self-explanatory; axisAC and point B represent 0% and 100% methyl methacrylate, respectively;axis AB and point C represent 0% and 100% butadiene, respectively, andaxis BC and point A represent 0% and 100% styrene, respectively. Ratiosof monomers falling above line DE tend to form interpolymers whichexhibit blocking, while ratios which fall below line DE tend to forminterpolymers which do not exhibit blocking. It should be appreciatedthat the line between blocking and nonblocking interpolymers is not asharp one, thus explaining why part of the shaded area extends aboveline DE. The important consideration is to selecting monomer ratioswhich, when plotted on the ternary diagram of FIG. 1, will fall withinthe shaded area, thus assuring that a non-blocking, film-forminginterpolymer will result. A preferred embodiment of the presentinvention is a latex in which the ratio by weight of methyl methacrylateto the combined Weight of butadiene and styrene is one to one, and theratio by weight of butadiene to styrene is one to one.

The latex may be prepared merely by mixing the various monomers in thedesired ratio with water in the presence of an emulsifying agent(surfactant) and polymerizing, following procedures and using equipmentwell known in the art. A polymerization catalyst may be used if desiredas is known in the art. It is also possible to prepare a graft latexwhereby a methyl methacrylate latex is formed first which acts as asubstrate onto which the butadiene and styrene are grafted. In preparingthe latex, the ratio of solids to water may vary over a wide range, butfrom an economic standpoint the ratio should be as high as possible,consistent with ease of handling and non-formation of fiocs. Typicallylatexes of the preferred embodiment of the present invention containabout 40% or more solids by weight.

The preferred emulsifying agent of the present invention is acombination of a fatty acid soap with an alkyl sulfate salt or an alkylaryl sulfonate salt. In preparing a latex it is, of course, desirable toobtain as high a solids content as possible with as low a surfactantdosage as possible. However, for certain uses such as in the productionof electrostatic sheets, binder plates, and like products, the amount ofalkyl sulfate or alkyl aryl sulfonate required to obtain a high solidslatex renders such latices unsuitable for their intended use. Thusquantities of sulfates and/or sulfonates substantially in excess ofabout 0.5 percent cause degradation of the latex electrical propy ertiesrendering the latex unsuitable for the production of electrostaticsheets and binder plates. Accordingly, fatty acid soaps have beenemployed in the production of polymers for this purpose since they donot adversely affect the latex electrical properties. Nevertheless,excessive quantities of such soaps are required to produce a latex ofonly about 35% solids. Attempts to increase the solids content byfurther increases in soap concentration have lead to coagulation due tothe extremely small micelles formed. Attempts to utilize very lowconcentrations of sulfactants have resulted in low solids latices andindeed, in unstable latices which also were subject to coagulationdilficulties.

It has been discovered that very small amounts of alkyl sulfate salts oralkyl and sulfonate salts, when mixed with fatty acid soaps, provide asynergistic effect. The total quantity of surfactant required to obtaina stable methyl methacrylate-butadiene-styrenc latex is greatly reduced,yet, much h gher solids contents are obt i ed i the latex.

.T he alkyl group of the alkyl sulfate salt or the alkyl aryl sulfonatesalt contains from 8 to 18 carbon atoms and preferably from 10 to 14carbon atoms. The akyl sulfates or alkyl aryl sulfonates are used in theform of their salts such as an alkali metal or ammonium salt. Thepreferred salts are the potassium, sodium and ammonium salts. A mixtureof alkyl sulfates may be used, such as is obtained from the sulfate saltof the alcohol mixture prepared by hydrogenating coconut oil. Inaddition, mixtures of alkyl aryl sulfonates, or mixtures of sulfates andsulfonates may be used.

Specific examples of alkyl sulfate salts useful as emulsifying agents inthe present invention are sodium lauryl sulfate, sodium cetyl sulfate,potassium lauryl sulfate, ammonium lauryl sulfate and sodium octylsulfate. Typical examples of alkyl aryl sulfonates useful in the presentinvention are sodium dodecyl benzene sulfonate, potassium dodecylbenzene sulfonate, sodium lauryl benzene sulfonate, potassium laurylbenzene sulfonate and ammonium dodecyl benzene sulfonate. The aboveexamples are cited as illustrative and are in no way limiting.

The soaps used in combination with alkyl sulfate salts or alkyl arylsulfonate salts are the water-soluble salts of the alkyl fatty acidshaving from 8 to 18 carbon atoms. It is preferred that the soap containfrom 8 to 12 carbon atoms and most preferred are capric and lauric acidsalts. The salts of the fatty acids constituting the soaps used in theinstant invention are the alkali metal and ammonium salts of such fattyacids. The preferred salts for the purposes of the present invention arethe potassium, sodium and ammonium salts. Mixtures of fatty acids may beused in preparing the soaps. In any event, the soap may be added as suchor the free fatty acid and the desired alkali or mixture of alkalisadded separately in the polymerization recipe to form the soap in situ.When forming the soap in situ, the alkalis should be present in anamount at least slightly in excess of the stoichiometric amount. Aminesalts of alkyl sulfates, alkyl aryl sulfonates and alkyl fatty acidsoaps have also been found to be very good emulsifiers when used inplace of the alkali metal and ammonium salts. However, it has been foundthat alkanolamine salts, such as diethanolamine lauryl sulfate,deleteriously effect the electrostatic acceptance of the interpolymerfilms. Thus alkanolamine salts should be avoided when preparing latexesto be used as coating compositions in the preparation of electrostaticsheets and binde plates.

'In accordance with the present invention, polymerization mixtures areprepared which contain from about 0.5 to about 2.5 percent by weight ofsurfactant based on the total weight of monomers to be polymerized. Theyield of latex solids, i.e., the methyl methacrylate-butadienestyreneinterpolymer, is of course, generally less than 100 percent due tomonomer losses, etc. Nevertheless, a low surfactant latex is produced inaccordance with the present invention which contains no more than about2.5 percent by weight of surfactant based on the weight of latex solidsor resin. As used herein, the term weight of the surfactant is the sumof the weight of the acid from which the fatty acid soap is derived andthe Weight of the sulfate salt, sulfonate salt, or sulfate-sulfonatesalt mixture. Stable latices may be prepared in accordance with theinvention in which the surfactant content is about 0.5 percent by weightbased on the weight of latex solids or resin.

The weight ratio of acid to sulfate or sulfonate needed to obtain astable latex will vary with the weight of the surfactant and, to alesser extent, with the specific materials in the surfactant. The totalquantity of sulfate and/ or sulfonate in the surfactant should notexceed about 0.5 per cent by weight based on the total weight of themonomers. larger quantities adversely affect the electrical propertiesof the latex and render it unsuitable for use in the production ofpolymeric coatings for electrostatic sheets and binder plates. Ingeneral, the amount of fatty soap should exceed the total amount ofsulfate and/or sulfonate, although such is not absolutely essential inthe very low ranges of surfactant. Nevertheless, the preferred and quitesuperior polymerization system, for the purposes of the presentinvention, is one in which the total surfactant is about 1 percent, andstill more preferably, below 0.75 percent with the amount of fatty acidsoap being substantially greater than the amount of sulfate and/ orsulfonate. Thus, the superior polymerization system includes surfactantin an amount in the range betwen about 1.0 to about 2.5 percent, andpreferably, less than about 1.5 percent in which the surfactant consistsof a major amount of the fatty acid soap and a minor amount of thesulfate and/or sulfonate salt.

Very minor amounts of the sulfonates and/or sulfates permit very greatreductions in the amount of fatty acid soap required to obtain a stablelatex of high solids content. Thus, quantities on the order of less than0.5 are an effective amount of sulfate and/or sulfonate to permitpreparation of a 50 percent solids latex in which the total surfactantcontent is on the order of about 1.5 weight percent.

In preparing binder plates, any of the conventional photoconductivepigments may be used with the aqueous latex. Such pigments include,without limitation, those set forth by Sugarman et al. in US. 2,862,815and include, for example, the colored oxides, sulphides, selenides,tellurides and iodides of cadmium, mercury, antimony, bismuth, thallium,idium, molybdenum, aluminum, lead and zinc. In addition, arsenictrisulphide, cadmium arsenide, lead chromate and selenium may be used.Particularly preferred as the photoconductive pigment are zinc oxide,tetragonal lead monoxide, the sulfides and selenides of zinc andcadmium, and mixtures of zinc oxide and red mercuric sulfide. Thepigment is first dispersed in water using a dispersing aid such aspotassium tripolyphosphate. The pigment dispersion is then blended withthe latex in the desired ratio, the solids content adjusted, and thecoating mixture applied to the substrate using conventional coatingequipment as an air knife, roller, dip blade, etc. If desired, aphotographic sensitizing dye may also be added to the coating to improvethe light sensitivity of the coating. The use of such dyes is set forth,for example, in US. 3,051,569 to Sugarman et al. and in US. 3,052,540 toGreig. The ratio of pigment to binder in the coating mixture is notcritical. The ratios normally used in the art range from 1 to 8 parts ofpigment to one part of binder. The precise ratio used will varyaccording to the end use and other considerations of the formulator. Ingeneral, a ratio of from about 1.5 to parts of pigment to one part ofbinder is preferred.

The economies possible by the use of the aqueous coating mixture of theinvention are most clearly realized when the coating is applied to apaper web and accordingly this constitutes a preferred embodiment of theinvention. However, the invention is not limited thereto and the coatingcomposition may be applied to any type of substrate as is conventionalin the art. It is preferred that the substrate be electricallyconductive or semiconductive as for example, paper, metal,electricallyconductive plastic, or plastic or glass coated with anelectrically conductive layer. If desired, the coating may also beapplied to a completely insulating substrate in which case a specialcharging device must be utilized to supply an artificial ground plate asis necessary in xerographic processes. Such a device, termed a doublecorona, is described, for example, in US. 2,922,883. Where paper is usedas the substrate, the paper itself may be first coated with a subbinglayer or may be otherwise treated as by addition of hygroscopic salts,carbon black, metallic powders, etc., to impart a higher degree ofelectrical conductivity to the paper web. Wet strength resins, dyes andother additives normally added in the paper-making process may be usedwithout detracting from the utility of the web to serve as the sub-EXAMPLE 1 A polymerization vessel was charged with the followingingredients:

Parts by weight Methyl methacrylate 50 Styrene 25 Butadiene 25 Capricacid 2.5 NH OH (28% aqueous sol.) 1.0 K S O 0.2 Sodium lauryl sulphate0.1 Dodecyl mercaptan 0.012 Water 125.0

This mixture was polymerized at 65 C. for 18-24 hours while beingagitated at a Pfaudler intensity of 2.0. The resultant latex was a flocfree, fluid material having a Hamilton-Beach stability of at least 7minutes.

EXAMPLE 2 A polymerization vessel was charged with the followingingredients:

Parts by weight Methyl methacrylate 50 Capric acid 2.5 NH OH (28%aqueous sol.) 1.0 K S O 0.2 Sodium lauryl sulphate 0.1 Water 125.0

This mixture was polymerized at 65 C. for 16-18 hours after which 25parts by weight styrene and 25 parts per weight butadiene were added andthe polymerization was continued for an additional 12 to 16 hours. As inexample 1, polymerization was conducted under agitation at a Pfaudlerintensity of 2.0. The latex thus prepared was a floc free fluid mixturehaving a Hamilton-Beach stability of at least 7 minutes.

Electrostatic sheets were prepared, using the latexes of Examples 1 and2, by applying the latex to enamelcoated or bond paper, usingconventional equipment and porcedures known in the art, as for example,a Warren Air Knife. The films were dried at C. to C. for two minutes andconditioned for 24 to 48 hours before testing. The same procedure may befollowed for preparing binder plates, except. that a photoconductivematerial, i.e., zinc oxide, should be incorporated into the latex beforeapplication of the latex to the paper substrate. In the preferredembodiment of the present invention the coating weight of thenonpigmented electrostatic sheets is preferably within the range of 3 to10 pounds dry weight per ream, however, good electrostatic propertiesare obtained with sheets coated with from 1.5 to 18 pounds dry weightper ream. The coating weight for zinc oxide pigmented binder plates ispreferably within the range of 20 to 22 pounds dry weight per ream.

When coated on paper, the latexes of the present invention form a clear,non-yellowing, cohesive, non-blocking film. The films are found not toyellow even after exposure to an 8-1 sun lamp for 400 hours.

Paper sheets 4 in. by 6 in., coated with 8 to 10 pounds dry weight perream of the latex of Example 1 were subjected on the coated side, to anegative voltage of 6500 TABLE I Percent V1 V2 retained relativehumidity, 72 hours 1, 900 950 50 50% relative humidity, 72 hours 1, 500850 57 75% relative humidity, 72 hours 1, 050 690 06 It was found thatthe electrostatic properties of coated sheets were not unduly effectedby varying the film weight from 1.5 to 10 pounds per ream, and therelative humidity form 0 to 75% Paper sheets were coated with 2 to 18pounds dry weight of the latex of Example 1, and subjected to a negativecharge of 6500 volts at a relative humidity of about 47 to 53%. Thecharge accepted and the charge retained after 2 minutes were measured;the results are shown in graphic form in FIG. 2. A coating which acceptsover 600 volts and retains over 50% of that charge for 2 minutes isconsidered to have excellent electrostatic properties. As is shown inFIG. 2 sheets coated with the latex of the present invention exhibitexcellent charge acceptances and retention properties. It is also notedthat while sheets coated with smaller amounts of the latex acceptance asmaller percentage of the charges than sheets coated with larger amountsof the latex, sheets coated with smaller amounts of the latex retain ahigher percentage of the charge, thus permitting the use of smalleramounts of the coating than would be possible if the percentage of thecharge retained was uniform for all coating weights.

Blocking was tested by coating paper sheets with the latexes of thepresent invention and forming films as herein described. Sheets 4 inchesby 4 inches were placed with the coated side in contact with a glassplate, and a weight was placed on the glass plate so as to subject thesheet to 1 pound per square inch pressure. This assembly was placed inan oven and held at 70 C. for four hours, at the end of which time theassembly was removed from the oven and allowed to cool. If the sheetsfell away from the glass plate without adhering thereto, no blocking wasobserved. Coatings made in accordance with the present inventionexhibited substantially no blocking.

The binder plates and electrostatic sheets produced as herein describedhave excellent flexibility, tensile strength and bonding strength.Highly adherent coatings may be produced on a variety of substrates. :Ifdesired, plasticizers may be added to the latex, but their use is notnecessary. The binder plates and electrostatic sheets may be overcoatedby a thin layer of protective resin, as known to those skilled in theart.

Prints were made on the electrostatic sheets of the present invention byimposing a voltage through a needle point onto the coated paper anddeveloping the thus formed latent image in the usual manner aspreviously described. Prints were also made on the binder plates of thepresent invention in the usual manner by charging the paper in the dark,exposing it under white light and printing following the usualElectrofax process as previously described. In either case, clear, sharpprints were obtained of at least equal quality to those obtained usingprior art electrostatic sheets and binder plates.

What is claimed:

1. A coating composition for use in preparing coated sheets comprisingan aqueous latex, said latex having dispersed therein an interpolymer ofmethyl methacrylate, butadiene and styrene, the ratio by Weight of saidmethyl methacrylate to said butadiene to said styrene being selected sothat the proportion of these monomers is represented by a point whichfalls within the shaded area of the ternary diagram of FIG. 1, and saidlatex further containing dissolved therein from about 0.5 to about 2.5percent by Weight of a surfactant consisting essentially of a mixtureof:

(A) an amount up to 0.5 percent by weight and effective to exert, withsalt (B) specified hereinbelow, a synergistic dispersing effect, of asalt selected from the group consisting of the alkali metal and ammoniumsalts of alkyl sulfates, alkyl aryl sulfonates and mixtures thereof, thealkyl groups of said salts containing from 8 to 18 carbon atoms, and

(B) an effective amount, at least equal to the amount of salt (A) of asalt selected from the group consisting of the alkali metal and ammoniumsalts of fatty acids containing from 8 to 18 carbon atoms, the amount ofsaid fatty acid salt exceeding the amount of salt (A) when the totalsurfactant is less than about 0.75 percent by weight,

the quantities of said surfactant and the components thereof being basedon the Weight of interpolymer, with the amount of salt (B) calculated asthe weight of fatty acid from which salt (B) is derived.

2. Process for emulsion polymerization of methyl methacrylate, butadieneand styrene, the ratio by weight of said methyl methacrylate to saidbutadiene to said styrene being selected so that the proportion of thesemonomers is represented by a point which falls within the shaded area ofthe ternary diagram of FIG. 1, comprising charging said monomers into apolymerization vessel, and polymerizing in a medium comprising water,said Water constituting no more than about 60 percent by weight of thepolymerization mixture, and from about 0.5 to about 2.5 percent byweight based on monomer, of a surfactant, said surfactant consistingessentially of a mixture of:

(A) an amount up to 0.5 percent by weight and effective to exert, withcomponent (B) specified hereinbelow, a synergistic dispersing effect; ofa salt selected from the group consisting of the alkali metal andammonium salts of alkyl sulfates, alkyl aryl sulfonates and mixturesthereof, the alkyl groups of said salts containing from 8 to 18 carbonatoms, and

(B) an effective amount, at least equal to the amount of salt (A) of asalt selected from the group consisting of the alkali metal and ammoniumsalts of fatty acids containing from 8 to 18 carbon atoms, the amount ofsaid fatty acid salt exceeding the amount of salt (A) when the totalsurfactant is less than about 0.75 percent by weight,

the quantity of said surfactant being calculated as the sum of theweight of salt (A) and the weight of fatty acid from which salt (B) isderived whereby a stable, low

surfactant latex containing at least about 40 percent by atoms and fattyacid salt (B) contains from 8 to 12 car bon atoms.

'6. The coating composition of claim 1 in which said salt (A) is analkyl sulfate salt.

7. The coating composition of claim 1 in which said salt (A) is an alkylaryl sulfonate salt.

8. A process in accordance with claim 2 wherein the alkyl group of salt(A) contains from 10' to 14 carbon atoms and fatty acid salt (B)contains from 8 to 12 carbon atoms.

9. A process in accordance with claim 2 wherein said salt (A) is analkyl sulfate salt.

9 10 10. A process in accordance with claim 2 wherein said 3,320,2045/1967 Blanchard et a1. 260-80.7 salt (A) is an alkyl aryl sulfonatesalt. 3,406,133 10/ 1968 Hartshorn 260--80.7

References Cited FOREIGN PATENTS UNITED STATES PATENTS 5 1,351,3473/1963 France 260-80.7

2,744,099 5/1956 Mitchell et al. 26080.7 3,078,260 2/1963 Hayes DONALDARNOLD, Prlmary Exammer 3,142,654 7/1964 Peterson et a1 26029.7T US ClXR 3,176,037 3/1965 Warner 260-807 3,256,233 6/1966 Hahn 812211260-29.7T 10 1

